In the development of satellite technologies, appendage flexibility and configurability often affect the types of missions which can be performed by the satellite and define the variety of environments in which the satellite can operate. As more exotic mission applications are developed, appendages and appendage deployment subsystems are optimized to specifically tailor satellites to particular missions.
One known application in which specialized appendages have been designed relates to optical systems. As spacecraft capabilities and mission applications require increased optical capabilities, large, multi-panel, sun-oriented deployable optical elements have been developed. The development of deployable systems has further necessitated a conventional engineering solution to deploy photovoltaic arrays or other appendages, such as mirrors, in an extremely precise yet highly repeatable manner. See, e.g., P. Alan Jones & Brian R. Spence, Spacecraft Solar Array Technology Trends, available at <http://www.aec-able.com/corpinfo/Resources/PAJ-IEEE-98.pdf> (last visited Jun. 16, 2004).
Conventional appendage deployment systems utilize a combination of highly rigid hinges and latches to deploy appendages with a high degree of precision. When deployed, these appendages are positioned and oriented very accurately relative to the main spacecraft body. In theory, the combination of the hinge axis of rotation and the position of the latch when closed should supply adequate rigidity and repeatability, required by the latest generation of spacecraft with large, deployable appendages.
In practice, however, it is difficult and expensive to build conventional rigid hinge-latch systems which can provide the rotational capability needed prior to full deployment, along with the precision and rigidity required following deployment. Furthermore, it is extremely difficult and time consuming to install conventional hinges of this type on the spacecraft with their rotation axes correctly aligned so the appendages do not bind during deployment. Conventional precision hinges also tend to have extremely tight mechanical tolerances in order to minimize any free-play, making them even more expensive to manufacture, and also causing high rotational friction levels. Finally, conventional rigid hinges are highly susceptible to damage, since their precision mechanisms often cannot handle high launch load stresses.
FIG. 1 depicts a conventional deployment hinge, in a state where the hinge has fully deployed an appendage. Specifically, conventional deployment hinge 101 is permanently mounted on satellite 102, and appendage 104 has been deployed by fully opening deploying conventional deployment hinge 101, so that appendage 104 rests against satellite 102. The arrows depicted at the center of appendage 104 illustrate residual forces and torques caused by conventional deployment hinge 101, due to the lingering physical contact between conventional deployment hinge 101 and appendage 104. These lingering residual forces affect the precise positioning of appendage 104. In the case where appendage 104 is a photovoltaic solar cell array or mirror, these lingering forces can degrade operational capabilities and prevent satellite 102 from successfully performing a mission.
It is therefore considered highly desirable to provide an improved apparatus for repeatedly and accurately deploying an appendage. In particularly, it is desirable to provide an enhanced deployment hinge which allows a hinge to be removed from the mechanical load path of the deployed, latched appendage, without interference from residual forces or torques associated with the hinge.